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If the sum of two numbers is 11, and the sum of their squares is 99, find the sum of their cubes.

+1 vote
652 views
If the sum of two numbers is 11, and the sum of their squares is 99, find the sum of their cubes.
posted Sep 3, 2015 by Upma

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4 Answers

+1 vote
 
Best answer

a+b = 11
a^2+b^2=99
=>
(a+b)^2 = a^2+b^2+2ab
121=99+2ab
or
ab=11

Now lets look at
(a+b)(a^2+b^2) = a^3+ab(a+b)+b^3
11*99 = a^3+b^3+11*11
a^3+b^3 = 968

answer Sep 4, 2015 by Salil Agrawal
+2 votes

Answer is 968

answer Sep 4, 2015 by Manoj Suryawanshi
0 votes

answer is 1210

answer Sep 3, 2015 by Justine Mtafungwa
0 votes

x+y=11
x(Square)+y(Square)=99
121-99=2xy
xy=11
x(Cube)+y(Cube)=11(99-11)
=11*88
=968

answer Sep 4, 2015 by anonymous
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